1. Field of the Invention:
This invention relates generally to attachments for use with metalworking lathes, and more particularly to an adjustable precision live center for use with metal working lathes.
2. Background Art:
Lathes are widely used to cut and remove tapers from shafts, tubes, and pipes, hereinafter collectively referred to as "workpieces". In a typical lathe, a workpiece is coupled between the chuck and the tailstock of the lathe. As the lathe rotates the workpiece, a tool post is advanced towards the chuck, removing material from the workpiece. If, however, the chuck and the tailstock are not perfectly aligned, the tool post will cut a taper in the circumference of the workpiece.
More specifically, if the tailstock of the lathe is positioned closer to the tool post than the chuck of the lathe, then the end of the workpiece that is coupled to the tailstock will be cut to a smaller diameter than the end of the workpiece coupled to the chuck end of the lathe. Conversely, if the tailstock is positioned farther from the tool post than the chuck end of the lathe, the end of the workpiece coupled to the tailstock will be cut to a diameter larger than the end of the workpiece coupled to the chuck of the lathe. Thus, in one instance the diameter of the workpiece gradually increases along the length of the workpiece from tailstock to chuck, and in the other instance the diameter of the workpiece decreases along the length of the workpiece from tailstock to chuck. Often, the object of lathe work upon shafts, tubes, and pipes is to remove all tapers to provide a perfectly uniform shaft, tube, or pipe, so a tapered workpiece is unacceptable.
Of course, such defects may be corrected through adjustment of the lathe tailstock relative to the lathe chuck. To remove an unwanted taper, the tailstock must be physically adjusted before another pass can be made with the tool post. Often, actuation of the means for adjusting the position of the tailstock relative to the chuck will introduce as much, if not greater, error than that sought to be corrected by the adjustment. More specifically, the various levers, adjustment wheels, and threaded screws do not allow for precision adjustment, and often introduce additional unwanted taper into the workpiece. Thus, the manufacture of a workpiece often requires several passes of the lathe, many of which are required due to the crudeness of the adjustment features present in most lathes. This process is time consuming, often requiring half an hour to forty-five minutes of lathe work to fully remove the taper from a workpiece. This process can only be characterized as an inefficient and sloppy convergence.
Moreover, the repeated adjustment of the tailstock may result in damage to the adjustment means. For example, adjustment screws may become stripped through repeated use. When such damage occurs, the lathe is completely useless, and a time-consuming and expensive repair job must be undertaken to restore the lathe to operation.
A variety of prior art live and dead center lathe tools exist for coupling between the tailstock of the lathe and the workpiece which allow for the lateral adjustment of the workpiece relative to the lathe. However, these prior art lather tools generally are unsuitable for high speed precision work, and often lack sufficient stability.
U.S. Pat. No. 1,319,585 for Lathe Tool granted Oct. 21, 1919 to L. E. Hunt discloses a "dead center" lathe tool that allows for the lateral adjustment of the tailstock assembly. Since it is a "dead center" having no bearings it is not rotatable at high speeds. Moreover, the lateral adjustment mechanism is spring-biased, so this device is not a precision instrument.
U.S. Pat. No. 1,358,164 for Lathe Center granted Nov. 9, 1920 to V. A. Cottinger discloses a lathe center that allows for the lateral adjustment of the workpiece without adjustment of the tailstock. The overall length of this lathe center renders it unstable, and thus unsuitable for precision work.
U.S. Pat. No. 3,593,602 for Taper Attachment for A Turning Lathe granted July 20, 1971, to S. J. Westrom discloses a taper attachment that allows for the lateral adjustment of the lathe center relative to the tailstock through operation of a sliding plate assembly, which renders the apparatus unsuitable for high speed precision work.
U.S. Pat. No. 3,630,112 for Machine Tool Center granted Dec. 28, 1971 to K. J. Sudholt discloses a machine tool center that allows for the lateral adjustment of the lathe center relative to the tailstock by operation of a worm gear arrangement, which renders the apparatus unsuitable for precision work.